Volume 103, Issue 5, May 1998
Index of content:
- NONLINEAR ACOUSTICS, MACROSONICS 
103(1998); http://dx.doi.org/10.1121/1.422750View Description Hide Description
A finite element method(FEM) is presented for the study of nonlinear acoustic standing waves inside a chamber. The method is developed using the Galerkin–Bubnov weighted residual formulation and applied to solve the Lagrangian second-order wave equation, including thermal and viscous dissipation terms. A one-dimensional problem is studied in the frequency domain. Numerical data are compared with analytical results obtained by using a perturbation scheme for the cases of resonance and antiresonance in a rigid-walled tube with one-sided rigid or pressure release boundary condition. The FEM algorithm is shown to be well suited for the study of high-frequency standing wave fields in which the effect of absorption cannot be described by simple analytical expressions.
103(1998); http://dx.doi.org/10.1121/1.422751View Description Hide Description
A general theory of the (Langevin) acoustic radiation force in three-dimensional fields in lossless fluids in Eulerian and Lagrangian coordinates is given. It is based on Brillouin’s approach of an acoustic radiation stress identified in Eulerian coordinates with the negative time average of the momentum flux density and in Lagrangian coordinates with the time average of the Piola–Kirchhoff–Boussinesq stress. It is shown in comparison to other statements from the literature that these stresses are not in general identical but that in the linear-acoustics approximation, the difference between the results in the two representations vanishes if the radiation force acting on an object entirely surrounded by the sound-propagating fluid is considered. It is just this situation which is of experimental relevance.